const telegramPassport = new TelegramPassport("<bot_private_key>");

const data = telegramPassport.decryptPassportData(
    update.message.passport_data
);

// the nonce is retuned within the RequestedFields object

const nonce = data.nonce;

/*
get the data corresponding to the file you want to decryp
for example, the front side of the id card
*/

const id_frontSide = data.identity_card.front_side;

// download the file using the getFile API endpoint

...

// decryp the file

const file = telegramPassport.decryptData(
  downloaded_file_data,
  id_fronSide.secret,
  id_fronSide.file_hash,
);

/*
in this case, data will look like this

data: [
  {
    "type": "phone_number",
    "phone_number": "XXXXXXXXXXX",
    "hash": "the_base64-encoded_hash",
  },
  {
    "type": "email",
    "email": "[email protected]",
    "hash": "the_base64-encoded_hash"
  },
]
*/

// decrypt the credentials

const credentials = telegramPassport.decryptPassportCredentials(
  update.message.passport_data.credentials,
);